Dual emitting device for active matrix organic electroluminescence

ABSTRACT

An organic electroluminescence (EL) device is provided, including a transparent substrate and an array of pixels over the transparent substrate. Each of the pixels includes at least one first sub-pixel and at least one second sub-pixel, wherein the at least one first sub-pixel each includes a first organic light emitting diode for providing light in a first direction, and the second sub-pixel each includes a second organic light emitting diode for providing light in a second direction substantially opposite to the first direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of pending U.S. patent application Ser.No. 10/911,483, filed on Aug. 5, 2004 and entitled “Dual emitting methodand device for active matrix organic electroluminescence,” the entiretyof which is incorporated by reference herein.

TECHNICAL FIELD

The disclosure relates in general to an electroluminescence device and,more particularly, to a structure of an organic electroluminescencedevice including a single display panel for dual-display and a method ofmanufacturing the same.

BACKGROUND

Flat panel display (“FPD”) devices may include liquid crystal display(“LCD”) devices and electroluminescence (“EL”) devices. An EL device isa device which makes use of the phenomenon of electroluminescence toemit light. An EL device generally includes thin film transistors(“TFT”) and an organic light-emitting diode (“OLED”) further including alight-emitting layer. When a current passes between a cathode and ananode of the OLED device, light is emitted through the light-emittinglayer.

Conventional organic EL devices can be designed to include two panelsfor dual display or double display: a main panel and a sub-panel.Generally, the main panel serves to provide main display functions of anelectronic product, and the sub-panel serves to provide subsidiarydisplay functions such as a caller identity display or a clock display.The main panel and the sub-panel are generally independent of eachother, and include individual substrates, resulting in a disadvantageousincrease in device size.

SUMMARY

Embodiments consistent with the disclosure provide for an organic ELdevice on a single substrate that provides a dual display function,whereby a device size is reduced.

To achieve these and other advantages, and consistent with the purposeof the disclosure as embodied and broadly described, there is providedan organic electroluminescence (EL) device, including a transparentsubstrate and an array of pixels over the transparent substrate. Each ofthe pixels includes at least one first sub-pixel and at least one secondsub-pixel, wherein the at least one first sub-pixel each includes afirst organic light emitting diode for providing light in a firstdirection, and the second sub-pixel each includes a second organic lightemitting diode for providing light in a second direction substantiallyopposite to the first direction.

Consistent with the disclosure, there is also provided an organicelectroluminescence (EL) device including a transparent substrate and anarray of pixels over the transparent substrate, each pixel including atleast one first sub-pixel and at least one second sub-pixel, each pixelbeing in a respective pixel area, wherein each pixel area furtherincludes at least one first area each for a corresponding firstsub-pixel and at least one second area each for a corresponding secondsub-pixel. Each pixel includes a first conductive layer over thesubstrate in at least the at least one first area, a second conductivelayer over the substrate in the at least one second area, an organic ELlayer over both the first conductive layer and the second conductivelayer in both the at least one first area and the at least one secondarea, a third conductive layer over the organic EL layer in the at leastone first area, and a fourth conductive layer over the organic EL layerin at least the at least one second area, wherein the first conductivelayer, the organic EL layer, and the third conductive layer in each ofthe at least one first area collectively form a corresponding firstsub-pixel, and the second conductive layer, the organic EL layer, andthe fourth conductive layer in each of the at least one second areacollectively form a corresponding second sub-pixel, and wherein thefirst conductive layer and the fourth conductive layer are transparent.

Consistent with the disclosure, there is still provided a method ofmanufacturing an organic electroluminescence (EL) device includingproviding a transparent substrate, defining a first area and a secondarea on the transparent substrate, forming a transistor in each of thefirst and second areas, forming a first light reflecting layer over thesubstrate in the second area, forming a first transparent conductivelayer over the substrate in the first area and over the first lightreflecting layer, forming an organic electroluminescence layer over thefirst transparent conductive layer in both the first area and the secondarea, forming a second light reflecting layer over the organicelectroluminescence layer in the first area, and forming a secondtransparent conductive layer over the organic electroluminescence layerin at least the second area and over the second light reflecting layer.

Additional features and advantages of the disclosure will be set forthin part in the description which follows, and in part will be obviousfrom the description, or may be learned by practice of the disclosure.The features and advantages of the disclosure will be realized andattained by means of the elements and combinations particularly pointedout in the appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the disclosure, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thedisclosure and together with the description, serve to explain theprinciples of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a dual-display panel of an organic electroluminescence(“EL”) device consistent with an embodiment of the disclosure;

FIG. 2A shows a pixel arrangement of an organic EL device consistentwith an embodiment of the disclosure;

FIG. 2B shows a pixel arrangement of an organic EL device consistentwith another embodiment of the disclosure;

FIG. 3A is a cross-sectional view of a pixel of an organic EL deviceconsistent with yet another embodiment of the disclosure;

FIG. 3B is a cross-sectional view of a pixel of an organic EL deviceconsistent with still another embodiment of the disclosure; and

FIGS. 4A to 4F are diagrams showing a method of manufacturing an organicEL device consistent with an embodiment of the disclosure.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of thedisclosure, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIG. 1 is a schematic diagram of a dual-display panel 12 of an organicelectroluminescence (“EL”) device 10 consistent with an embodiment ofthe disclosure. Dual-display panel 12 is provided with an array ofpixels (not numbered). An exemplary pixel 14 includes a first set ofsub-pixels R₁, G₁ and B₁ for display of colors red, green and blue,respectively, and a second set of sub-pixels R₂, G₂ and B₂ for displayof colors red, green and blue, respectively. The first set of sub-pixelsR₁, G₁ and B₁ functions to provide image display in a first directionindicated by an arrow 16, and the second set of sub-pixels R₂, G₂ and B₂functions to provide image display in a second direction indicated by anarrow 18. In an aspect consistent with the disclosure, the firstdirection is substantially opposite to the second direction. Inoperation, the first sets of sub-pixels of all pixels may be coupled toreceive a first set of signals for collectively displaying a first imagein the first direction, and the second sets of sub-pixels of all pixelsmay be coupled to receive a second set of signals for collectivelydisplaying a second image in the second direction. The first set ofsignals and the second signals may be provided at the same time fordisplaying the first image and the second image simultaneously or atdifferent times for displaying the first image and the second image offfrom each other.

FIG. 2A is a diagram of an exemplary pixel arrangement of an organic ELdevice consistent with an embodiment of the disclosure. Sub-pixels R₁and R₂ are formed in a sub-pixel area that may otherwise be provided fora single sub-pixel for the color red display. Similarly, sub-pixels G₁and G₂, and sub-pixels B₁ and B₂ are formed in a single sub-pixel areathat may otherwise be provided for a single sub-pixel for display of thecolors green and blue, respectively. Sub-pixels R₁, G₁ and B₁ of a firstset of sub-pixels in pixel 14 are substantially aligned with oneanother. Likewise, sub-pixels R₂, G₂ and B₂ of a second set ofsub-pixels in pixel 14 are substantially aligned with one another. Thefirst set of sub-pixels R₁, G₁ and B₁ is substantially aligned with thesecond set of sub-pixels R₂, G₂ and B₂ in pixel 14.

FIG. 2B is a diagram of another exemplary pixel arrangement of anorganic EL device consistent with another embodiment of the disclosure.Sub-pixels R₁, G₁ and B₁ of a first set of sub-pixels in pixel 14 areformed in a delta arrangement. Likewise, sub-pixels R₂, G₂ and B₂ of asecond set of sub-pixels in pixel 14 are formed in another deltaarrangement. The first set of sub-pixels R₁, G₁ and B₁ are interleavedwith the second set of sub-pixels R₂, G₂ and B₂ in pixel 14.

Although only two different arrangements of the sub-pixels are shown inFIGS. 2A and 2B, it is to be understood that arrangement of thesub-pixels is not limited thereto and may be in any other form thanshown in FIGS. 2A and 2B. For example, the first set of sub-pixels maybe offset from the second set of sub-pixels. Further, consistent withthe disclosure, there may be provided two sets of pixels arranged in anysuitable form on a single substrate for displaying images in oppositedirections.

FIG. 3A is a cross-sectional view of a sub-pixel 30 of an organic ELdevice consistent with an embodiment of the disclosure. Sub-pixel 30,which corresponds to one of the first and second sub-pixels as describedabove, includes a thin film transistor (“TFT”) 32 and an organic lightemitting diode (“OLED”) 34. TFT 32 is used to drive OLED 34. The organicEL device including TFTs 32 and OLEDs 34 is also referred to as anactive matrix organic light emitting diode (“AMOLED”) device. TFT 32 andOLED 34 are formed on a transparent substrate 36 over which a layer ofsilicon nitride 38 and a layer of silicon oxide 40 are formed. TFT 32includes a semiconductor layer 32-1, a gate oxide layer 32-2, a gateelectrode 32-3, a source electrode 32-4 and a drain electrode 32-5.Semiconductor layer 32-1 may further include contact regions heavilydoped with, for example, p-type impurities for ohmic contact, and anactive region made of polycrystalline silicon. An inter-layer dielectric(“ILD”) 42 is provided to electrically isolate gate electrode 32-3 andsource and drain electrodes 32-4 and 32-5. A first passivation layer 44made of insulating material such as silicon nitride or silicon oxide isformed over substrate 36, exposing a portion of drain electrode 32-5 toserve as a contact hole.

OLED 34 includes a conductive layer 34-1, an organic electroluminescence(“EL”) layer 34-2 and a reflecting layer 34-3. Material of theconductive layer 34-1 such as indium tin oxide (“ITO”) to serve as anodeis formed to cover first passivation layer 44 excluding a portioncorresponding to TFT 32. A second passivation layer 46 is formed oversubstrate 36 to cover TFT 32. Organic EL layer 34-2, which may containlayers of organic materials, is formed over second passivation layer 46and the conductive layer 34-1. Material of the reflecting layer 34-3such as aluminum (Al) to serve as cathode is formed over organic ELlayer 34-2. When OLED 34 is driven by TFT 32, light radiating fromorganic EL layer 34-2 in part penetrates through the conductive layer34-1 and in part is reflected by the reflecting layer 34-3, resulting inlight emission through transparent substrate 36 in a first directionindicated by an arrow 48. In one aspect, sub-pixel 30 corresponds to oneof the first set of sub-pixels R₁, G₁ and B₁ shown in FIG. 2A or 2B.

FIG. 3B is a cross-sectional view of a sub-pixel 60 of an organic ELdevice consistent with another embodiment of the disclosure. Sub-pixel60, which corresponds to another one of the first and second sub-pixelsas described above, includes a thin film transistor (“TFT”) 62 and anorganic light emitting diode (“OLED”) 64. TFT 62, used to drive OLED 64,has a similar structure to TFT 32 and is not further described. TFT 62and OLED 64 are formed on transparent substrate 36 over which a layer ofsilicon nitride 38 and a layer of silicon oxide 40 are formed. OLED 64includes a conductive layer 64-1 to serve as an anode, an organicelectroluminescence (“EL”) layer 64-2 and a transparent conductive layer64-3 to serve as a cathode. Material of the conductive layer 64-1 suchas indium tin oxide (ITO) to serve as anode is formed over substrate 36.Organic EL layer 64-2 is formed over the conductive layer 64-1. Materialof the transparent conductive layer 64-3 such as indium zinc oxide(“IZO”) to serve as a cathode is formed over organic EL layer 64-2. Thetransparent conductive layer 64-3 has a thickness ranging fromapproximately 50 to 10,000 angstroms (A). In one aspect, a thinconductive layer 64-4 is formed over organic EL layer 64-2 before thetransparent conductive layer 64-3 is formed. The thin conductive layer64-4 includes, for example, aluminum, and is thin enough to remaintransparent to light. In another aspect, the thin conductive layer 64-4has a thickness of less than 500 angstroms (A), and the thickness may,for example, be 50 to 100 angstroms. A reflecting layer 64-5 is formedunderneath the conductive layer 64-1 for reflecting light emitted fromorganic EL layer 64-2. Thus, when OLED 64 is driven by TFT 62, lightradiating from organic EL layer 64-2 in part penetrates through thetransparent conductive layer 64-3 and in part is reflected by thereflecting layer 64-5, resulting in light emission through thetransparent conductive layer 64-3 in a second direction indicated by anarrow 66. In one aspect, sub-pixel 60 corresponds to one of the secondset of sub-pixels R₂, G₂ and B₂ shown in FIG. 2A or 2B. In anotheraspect, the second direction is substantially opposite to the firstdirection shown in FIG. 3A.

FIGS. 4A to 4F are diagrams showing a method of manufacturing an organicEL device consistent with an embodiment of the disclosure. Transparentsubstrate 36, such as a glass substrate, is formed by, for example,cleaning and impurity doping. A layer of silicon nitride 38 and a layerof silicon oxide 40 are formed on transparent substrate 36.

Referring now to FIG. 4A, a plurality of sub-pixel areas are defined ontransparent substrate 36. Each of the sub-pixel areas includes a firstsub-pixel area 30′ wherein sub-pixel 30 as shown in FIG. 3A is to beformed and a second sub-pixel area 60′ wherein sub-pixel 60 as shown inFIG. 3B is to be formed. Thin film transistors (“TFT”) 32 and 62 areformed in the first and second sub-pixel areas 30′ and 60′,respectively.

Referring to FIG. 4B, a reflecting layer 64-5 is formed in the secondsub-pixel area 60′. Reflecting layer 64-5 may comprise metal.

Referring to FIG. 4C, a conductive layer 34-1 of sub-pixel 30 is formedin the first sub-pixel area 30′ and a conductive layer 64-1 of sub-pixel60 is formed in the second sub-pixel area 60′. In one aspect, theconductive layer 34-1 and 64-1 may comprise ITO. The conductive layer34-1 serves as an anode electrode of OLED 34. The conductive layer 64-1and the reflecting layer 64-5 may together serve as an anode electrodeof OLED 64.

Referring to FIG. 4D, the organic EL layers 34-2 and 64-2 are formed inthe first sub-pixel area 30′ and the second sub-pixel area 60′,respectively. In one aspect, the organic EL layers 34-2 and 64-2 arepigmented with the same color. In another aspect, the organic EL layers34-2 and 64-2 are formed by depositing a layer of organic EL materialsin both the first and second sub-pixel areas 30′ and 60′.

Referring to FIG. 4E, the reflecting layer 34-3 is formed over theorganic EL layer 34-2 in the first sub-pixel area 30′. The reflectinglayer 34-3, such as an aluminum layer, serves as a cathode electrode ofOLED 34.

Referring to FIG. 4F, a transparent conductive layer 64-3 is providedover organic EL layer 64-2 to form a cathode of OLED 64 in the secondsub-pixel area 60′. In an aspect consistent with the disclosure, thetransparent conductive layer 64-3 is also formed over the reflectinglayer 34-3 of sub-pixel 30 in the first sub-pixel area 30′. In anotheraspect, the transparent conductive layer 64-3 may comprise IZO. In stillanother aspect, a thin conductive layer 64-4 may also be formed overorganic EL layer 64-2 of FIG. 3B before the transparent conductive layer64-3 is formed. The thin conductive layer 64-4 may comprise aluminum. Inone aspect, the thin conductive layer 64-4 has a thickness of less than500 angstroms. In another aspect, the thin conductive layer 64-4 is alsoformed over the reflecting layer 34-3 of sub-pixel 30 in the firstsub-pixel area 30′.

During the manufacturing process as discussed above, a plurality ofpixels may be simultaneously formed over substrate 36 to form a pixelarray. Each pixel may include a first set of sub-pixels each having thesame structure as sub-pixel 30 and a second set of sub-pixels eachhaving the same structure as sub-pixel 60, wherein the first set ofsub-pixels provides light in a first direction pointing towardssubstrate 36 as indicated by arrow 48 in FIG. 3A and the second set ofsub-pixels provides light in a second direction pointing away fromsubstrate 36 as indicated by arrow 66 in FIG. 3B.

Other embodiments of the disclosure will be apparent to those skilled inthe art from consideration of the specification and practice of thedisclosure disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the disclosure being indicated by the following claims.

What is claimed is:
 1. An organic electroluminescence device,comprising: a transparent substrate; and an array of pixels over thetransparent substrate, each of the pixels comprising at least one firstsub-pixel and at least one second sub-pixel, wherein the at least onefirst sub-pixel comprises a first organic light emitting diode emittingin a first direction, and the second sub-pixel includes a second organiclight emitting diode emitting in a second direction substantiallyopposite to the first direction.
 2. The device of claim 1, wherein thefirst organic light emitting diode comprises a conductive layer, areflecting layer, and an organic electroluminescence layer between theconductive layer and the reflecting layer.
 3. The device of claim 2,wherein the conductive layer comprises indium tin oxide (ITO) or indiumzinc oxide.
 4. The device of claim 2, wherein the reflecting layercomprises aluminum.
 5. The device of claim 1, wherein the second organiclight emitting diode comprises a reflecting layer, a transparentconductive layer, and an organic electroluminescence layer between thetransparent conductive layer and the reflecting layer.
 6. The device ofclaim 5, wherein the second organic light emitting diode comprises athin conductive layer between the transparent conductive layer and theorganic electroluminescence layer.
 7. The device of claim 6, wherein thethin conductive layer has a thickness of less than 500 angstroms.
 8. Thedevice of claim 5, wherein the transparent conductive layer has athickness of about 50 to 10000 angstroms.
 9. The device of claim 5,wherein the transparent conductive layer comprises indium tin oxide(ITO) or indium zinc oxide.
 10. The device of claim 1, wherein the atleast one first sub-pixel or the at least one second sub-pixel furthercomprises a thin film transistor.
 11. The device of claim 1, whereineach of the at least one first sub-pixels is aligned to a correspondingone of the at least one second sub-pixels.
 12. The device of claim 1,wherein the at least one first sub-pixel and the at least one secondsub-pixel are interleaved with each other.
 13. The device of claim 1,wherein the first sub-pixels are coupled to receive a first set ofsignals for collectively displaying a first image in the firstdirection, and the second sub-pixels are coupled to receive a second setof signals for collectively displaying a second image in the seconddirection.
 14. The device of claim 13, wherein the first and the secondimages are displayed at the same time.
 15. An organicelectroluminescence (EL) device, comprising: a transparent substrate;and an array of pixels over the transparent substrate, each pixelcomprising at least one first sub-pixel and at least one secondsub-pixel, each pixel being in a respective pixel area, wherein eachpixel area further comprises at least one first area for a correspondingfirst sub-pixel and at least one second area for a corresponding secondsub-pixel, each pixel comprising: a first conductive layer over thesubstrate in at least the at least one first area; a second conductivelayer over the substrate in the at least one second area; an organic ELlayer over both the first conductive layer and the second conductivelayer in both the at least one first area and the at least one secondarea; a third conductive layer over the organic EL layer in the at leastone first area; and a fourth conductive layer over the organic EL layerin at least the at least one second area, wherein the first conductivelayer, the organic EL layer, and the third conductive layer in each ofthe at least one first area collectively form a corresponding firstsub-pixel, and the second conductive layer, the organic EL layer, andthe fourth conductive layer in each of the at least one second areacollectively form a corresponding second sub-pixel.